Yes, I'm rembering that, of course :) Until now I never had hit the problem.User programs should include a workaround to that USERDEF stack
problem, to cope with bad TOS. They should use some private user stack
to avoid that trouble. I posted a (potentially unsafe) solution to
this list long ago, but it had poor success.
But I also rember it wasn't that easy to implement... On the other hand it's
an well known fact that the USERDEF function runs in super mode and
that there is little stack available... CFLIB/GEMLIB should handle it....